180 / 248
BEAM P
LUS FOR
N
EW
B
UILDINGS
I
NDOOR
E
NVIRONMENTAL
Q
UALITY
(I
EQ
)
V
ERSION
1.2
I
EQ
9
I
NCREASED
V
ENTILATION
Copyright © 2012 BEAM Society Limited. All rights reserved.
Page 159
Office of 1,000 m
2
and an occupant density of 9 m
2
per occupant. Using
the ASHRAE 62.1-2007 criteria results in a ventilation rate of 5.2
l/s/person, much less than previously accepted values of 8 or even 10 l/s
per person.
For simple systems where the outdoor air serves only a single space, or
a small number of similar spaces, the outdoor air flow rate can be
measured either:
using a pitot tube [ 5 ]
and manometer to perform a pitot tube
traverse in accordance with ASHRAE 111-98 [2] or
using an installed Wilson Flow Grid with a manometer.
The majority of systems will be too complex for such measurements and
the supply of outdoor air should be verified using a tracer gas
measurement. ASTM 741-00 [3]
describes the required properties of
tracer gases and discusses procedures for tracer decay, tracer step up
and constant concentration measurements.
S
YNERGIES
Air movement within spaces is dealt with under Thermal Comfort criteria.
Increased ventilation rates will have a negative impact on energy use,
particularly in a hot humid climate such as Hong Kong. Consideration
should be given to using heat recovery techniques to lessen the impact
or utilising CO
2
sensors in conjunction with the BMS to affect Demand
Control Ventilation (DCV).
5
International Organization for Standardization. ISO 3966-1977. Measurement of fluid flow in closed circuits - Velocity area
method using Pitot static tubes
.